As a general rule, transmission line effects become important if a circuit compo

Question

As a general rule, transmission line effects become important if a circuit component becomes

larger than 0.1 lambda, where lambda is the wavelength of the excitation. Using this rule, decide which of

the following situations require transmission line theory:

(a) A 60-Hz power line spans the 120-mile distance between Atlanta, GA, and Greenville,

SC. The velocity of propagation on the line is 8 × 107 m/s.

(b) A residential telephone line connects a home phone with a public digital network. The

distance from the home to the nearest switch is 100 m. The highest major frequency

component in transmitted speech is 2 kHz, and the velocity of propagation on the wire

is 5 × 107 m/s.

(c) The radio hardware of a cellular tower is located on the ground and uses long coaxial

cables to connect with the antennas at the top of 60 m towers. The operating frequency

is 1920 MHz, and the dielectric parameters of the coaxial cable are er = 5.3 and mr = 1.

(d) A memory chip is connected to a microprocessor on a computer motherboard with

4-cm microstrip lines. The velocity of propagation is 1.2 × 108 m/s, and the highest

harmonic content of the binary signaling is 3 GHz.

(e) A 25-ft Ethernet cable transmits binary signals with 100 MHz of maximum frequency

content between a router and a computer. The dielectric parameters of the cable are

er = 2.7 and mr = 1.

Explanation / Answer

a) it requires the transmission line theory 120 mile distance is given seems to be large.It requires long transmission line concept for its operation.

b) In this type of network you need only small length connecting wires as you usually use in your home accessories.So it doesn't require transmission line theory concept .

c) Here you may use short transmission line concept since transmission line frequency is very high which require strong coaxialcable connection not usually used in your home appliances.

D)This circuit is of electronics in nature working on lower voltages although frequency is high then also we don't need to connect through transmission line we need to connect it electronic bus wires and some kind of bread board circuit.Here you are using binary signals which also support my answer.

e) The same concept is used here as above here you are using binary signal .you are using 35 ft Ethernet cable which is also used in low voltage operations although frequency is high.

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